The objective of this project is to measure detection thresholds and operative scales of citrate taste judgement within spatially-matched, isolated, discrete regions of the anterior tongue tip in neurologically normal individuals. The anatomic characteristics of fungiform taste buds within the same site tested for citrate taste perception will be investigated using a non-destructive staining method and videomicroscopy. It is hypothesized that humans derive individual diversities of citrate taste sensitivity on the anterior tongue due, in part, to variations in taste bud density. Information from these studies will provide an objective method of measuring spatially discrete taste sensitivity in human, which when applied in the clinical setting, may be used to differentiate hypogeusias due to dystrophic (loss of taste buds) or dysfunctional (normal taste buds) aberrations caused by injury to the chorda-tympani nerve. Citrate detection thresholds and subjective strengths of taste intensity will be assessed in 85 healthy neurologically normal men and women between the ages of 16 and 45. A two-alternative forced choice, modified staircase procedure will be used to derive threshold. Cross-modal magnitude matching functions for taste intensity judgement will be obtained for five concentrations of citrate and measures of perceived strength will be determined. The right and left tongue tip surface will be tested to differentiate any side-to-side taste perception differences. Citrate solutions will be delivered to an enclosed, self- retained chamber reinforced to the surface of the tongue tip so that only a discrete and reproducible surface area of the tongue will be tested. The taste buds bathed by stimuli within the chamber will be distinguished by methylene blue stain and recorded by videomicroscopy. The number of fungiform papillae and pores per unit area will be determined so that the relationship of discriminative taste performance for a known number of taste buds can be examined. Comparisons of whole mouth (i.e., global) threshold and suprathreshold scales of citrate taste intensity will be made to elucidate the differences with spatially discrete taste perception.